The South Pole, Volumes 1 and 2 by Roald Amundsen

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It has thus been shown that the amount of warmth in that part of the
ocean which we call the Norwegian Sea varies from year to year. It
was shown by the Atlantic Expedition of the Michael Sars in 1910 that
the central part of the North Atlantic was considerably colder in 1910
than in 1873, when the Challenger Expedition made investigations there;
but the temperatures in 1910

[Fig. 13]

Fig. 13. -- Temperatures at one of the "Fram's" and one of the
"Challenger's" Stations, to the South of the South Equatorial Current
were about the same as those of 1876, when the Challenger was on her
way back to England.

We can now make similar comparisons as regards the South Atlantic. In
1876 the Challenger took a number of stations in about the same region
as was investigated by the Fram. The Challenger's Station 339 at the
end of March, 1876, lies near the point where the Fram's Station 44
was taken at the beginning of August, 1911. Both these stations lay in
about lat. 17.5deg. S., approximately half-way between Africa and South
America -- that is, in the region where a relatively slack current
runs westward, to the south of the South Equatorial Current. We
can note the difference in Fig. 13, which shows the distribution
of temperature at the two stations. The Challenger's station was
taken during the autumn and the Fram's during the winter. It was
therefore over 3deg. C. warmer at the surface in March, 1876, than in
August, 1911. The curve for the Challenger station shows the usual
distribution of temperature immediately below the surface in summer;
the temperature falls constantly from the surface downward. At the
Fram's station we see the typical winter conditions; we there find the
same temperature from the surface to a depth of 100 metres, on account
of cooling and vertical circulation. In summer, at the beginning of
the year 1911, the temperature curve for the Fram's station would
have taken about the same form as the other curve; but it would have
shown higher temperatures, as it does in the deeper zones, from 100
metres down to about 500 metres. For we see that in these zones it
was throughout 1deg. C. or so warmer in 1911 than in 1876; that is to
say, there was a much greater store of warmth in this part of the
ocean in 1911 than in 1876. May not the result of this have been
that the air in this region, and also in the east of South America
and the west of Africa, was warmer during the winter of 1911 than
during that of 1876? We have not sufficient data to be able to say
with certainty whether this difference in the amount of warmth in the
two years applied generally to the whole ocean, or only to that part
which surrounds the position of the station; but if it was general,
we ought probably to be able to find a corresponding difference in
the climate of the neighbouring regions. Between 500 and 800 metres
(272 and 486 fathoms) the temperatures were exactly the same in
both years, and at 900 and 1,000 metres (490 and 545 fathoms) there
was only a difference of two or three tenths of a degree. In these
deeper parts of the ocean the conditions are probably very similar;
we have there no variations worth mentioning, because the warming of
the surface and sub-surface waters by the sun has no effect there,
unless, indeed, the currents at these depths may vary so

[Fig. 14]

Fig. 14. -- Temperatures at one of the "Fram's" and one of the
"Valdivia's" Stations, in the Benguela Current. Much that there may
be a warm current one year and a cold one another year. But this is
improbable out in the middle of the ocean.

In the neighbourhood of the African coast, on the other hand, it looks
as if there may be considerable variations even in the deeper zones
below 500 metres (272 fathoms). During the Valdivia Expedition in 1898
a station (No. 82) was taken in the Benguela Current in the middle of
October, not far from the point at which the Fram's Station 31 lay. The
temperature curves from here show that it was much warmer (over 1.5deg.
C.) in 1898 than in 1911 in the zones between 500 and 800 metres
(272 and 486 fathoms). Probably the currents may vary considerably
here. But in the upper waters of the Benguela Current itself, from the
surface down to 150 metres, it was considerably warmer in 1911 than
in 1898; this difference corresponds to that which we found in the
previous comparison of the Challenger's and Fram's stations of 1876
and 1911. Between 200 and 400 metres (109 and 218 fathoms) there was
no difference between 1898 and 1911; nor was there at 1,000 metres
(545 fathoms).

In 1906 some investigations of the eastern part of the South Atlantic
were conducted by the Planet. In the middle of March a station was
taken (No. 25) not far from St. Helena and in the neighbourhood of the
Fram's Station 39, at the end of July, 1911. Here, also, we find great
variations; it was much warmer in 1911 than in 1906, apart from the
winter cooling by vertical circulation of the sub-surface waters. At
a depth of only 100 metres (54.5 fathoms) it was 2deg. C. warmer in 1911
than in 1906; at 400 metres (218 fathoms) the difference was over 1deg.,
and even at 800 metres (486 fathoms) it was about 0.75deg. C. warmer in
1911 than in 1906. At 1,000 metres (545 fathoms) the difference was
only 0.3deg..

From the Planet's station we also have problems of salinity,
determined by modern methods. It appears that the salinities at the
Planet station, in any case to a depth of 400 metres, were lower, and
in part much lower, than those of the Fram Expedition. At 100 metres
the difference was even greater than 0.5 per mille; this is a great
deal in the same region of open sea. Now, it must be remembered that
the current in the neighbourhood of St. Helena may be regarded as a
continuation of the Benguela Current, which comes from the south and
has relatively low salinities. It looks, therefore, as if there were
yearly variations of salinity in these

[Fig. 15]

Fig. 15. -- Temperatures at the "Planet's" Station 25, and the "Fram's"
Station 39 -- Both in the Neighbourhood of St. Helena

[Fig. 16]

Fig. 16. -- Salinities at the "Planet's" Station 25 (March 19, 1906)
And the "Fram's" Station 39 (July 29, 1911).

regions. This may either be due to corresponding variations in the
Benguela Current -- partly because the relation between
precipitation and evaporation may vary in different years, and partly
because there may be variations in the acquisition of less saline
water from the Antarctic Ocean. Or it may be due to the
Benguela Current in the neighbourhood of St. Helena having
a larger admixture of the warm and salt water to the west of it in
one year than in another. In either case we may expect a
relatively low salinity (as in 1906 as compared with 1911) to be
accompanied by a relatively low temperature, such as we have
found by a comparison of the Planet's observations with those of
the Fram.

We require a larger and more complete material for comparison; but even
that which is here referred to shows that there may be considerable
yearly variations both in the important, relatively cold Benguela
Current, and in the currents in other parts of the South Atlantic. It
is a substantial result of the observations made on the Fram's voyage
that they give us an idea of great annual variations in so important a
region as the South Atlantic Ocean. When the whole material has been
further examined it will be seen whether it may also contribute to
an understanding of the climatic conditions of the nearest countries,
where there is a large population, and where, in consequence, a more
accurate knowledge of the variations of climate will have more than
a mere scientific interest.

NOTES

NOTES

[1] -- Fram means "forward," "out of," "through." -- Tr.

[2] -- This retrospective chapter has here been greatly condensed, as
the ground is already covered, for English readers, by Dr. H. R. Mill's
"The Siege of the South Pole," Sir Ernest Shackleton's "The Heart of
the Antarctic," and other works. -- Tr.

[3] -- Anniversary of the dissolution of the Union with Sweden. -- Tr.

[4] -- Daengealso means "thrash." -- Tr.

[5] -- Unless otherwise stated, "miles" means English statute
miles. -- Tr.

[6] -- A language based on that of the country districts, as opposed
to the literary language, which is practically the same as Danish. The
maal is more closely related to Old Norse. -- Tr.

[7] -- Named after Dr. Nansen's daughter. -- Tr.

[8] -- A vessel sailing continuously to the eastward puts the clock
on every day, one hour for every fifteen degrees of longitude; one
sailing westward puts it back in the same way. In long. 180deg. one
of them has gone twelve hours forward, the other twelve hours back;
the difference is thus twenty-four hours. In changing the longitude,
therefore, one has to change the date, so that, in passing from east
to west longitude, one will have the same day twice over, and in
passing from west to east longitude a day must be missed.

[9] -- For the benefit of those who know what a buntline on a sail is,
I may remark that besides the usual topsail buntlines we had six extra
buntlines round the whole sail, so that when it was clewed up it was,
so to speak, made fast. We got the sail clewed up without its going to
pieces, but it took us over an hour. We had to take this precaution,
of having so many buntlines, as we were short-handed.